1. Technical Field
The present invention relates to semiconductor devices, and more particularly, to devices and fabrication methods that utilize atomic layer doping techniques.
2. Description of the Related Art
Throughout the evolution and advancement of computing devices, reducing their size and their power consumption while maintaining a high processing capacity have long been design goals. Transistors have been the cornerstone of electrical circuits of computing devices. A common transistor type is field-effect transistors (FET), in which the conductivity of a channel between terminals of the transistor is dependent on electric fields. Basic elements of an FET include a gate, a source and a drain, which are connected to conductive lines that control their operation through contacts. Planar FET transistors, which have been widely used in integrated circuits for the past several decades, were found to be increasingly inefficient on the nanometer scale. Reducing the size of the channel between the terminals of planar transistors to this scale leads to an inefficient leakage of current in the off-state of the transistor, resulting in an increase in power consumption in its idle state. Multiple gate field-effect transistors (MuGFET) have been developed to address this problem, as they incorporate several gates that surround the channel between a source and drain terminal of the transistor on a plurality of surfaces, thereby enabling the suppression of leakage current in the off-state.
There are several different types of multigate devices. FinFETs and Trigate devices are two examples. FinFET devices include a thin fin, which can be made of silicon, that provides the channel between a source and a drain. The fin can be overlaid with one or more pairs of gates, where the gates in a pair are on opposing sides of the fin. Trigates are similar to FinFETs in that they also employ fins. However, in a Trigate device, two vertical gates respectively envelope two separate fins and a single top gate is overlaid on the two vertical gates. The top gate usually extends across a plurality of transistor cells in trigate devices.